1. Field of the Invention
The present application relates to an electronic device, which is driven by a secondary battery (a chargeable battery), and a method controlling an electronic power supply for this electronic device.
The present application claims priority on Japanese Patent Application No. 2009-158764, filed Jul. 3, 2009; and on Japanese Patent Application No. 2009-163596, filed Jul. 10, 2009; the content of which is incorporated herein by reference.
2. Description of the Related Art
Conventionally, a technology is known which charges a secondary battery, which is embedded in an electronic device such as a digital camera, through a USB (Universal Serial Bus) cable. See, for example, Japanese Unexamined Patent Application, First Publication No. 2005-173822 (hereinafter referred to as Patent Document 1).
However, there is a limit on the amount of electric current provided from an external host device via a USB cable. This limit is based on a USB specification. Therefore, depending on the operation mode of digital cameras and the like, there is a problem in that the operation of charging a secondary battery cannot be controlled in an appropriate manner.
In addition, the power feeding capacity of a USB is specified as a predetermined rating. Therefore, there is a problem in that an operation, which requires a large amount of electric power exceeding the predetermined rating, cannot be performed appropriately while the secondary battery is being charged via a USB cable. For example, operations such as the driving of a lens barrel cannot be performed appropriately while the secondary battery is being charged via a USB cable.